Electromagnetic and laser treatment and cooling device

ABSTRACT

An apparatus for lowering the temperature of skin on a patient during treatment applying electromagnetic energy to the skin comprising a window of a first thermally conductive material through which electromagnetic energy can pass for placement against the epidermis of the skin. A reservoir of coolant is spaced from an edge of the window. A non-flowing second thermally conductive material connects the window and the reservoir to transfer heat from the window to the coolant in the reservoir.

TECHNICAL FIELD

This invention relates to electromagnetic and laser treatment devicesand more particularly to a cooling apparatus for use withelectromagnetic and laser devices to cool the human skin during thetreatment of patients.

BACKGROUND

The method of treating cutaneous lesions with light sources such aslasers is primarily based on the principal of Selective Photothermolysisproposed by Anderson (“Selective Photothermolysis: Precise Microsurgeryby Selective Absorption of Pulsed Radiation”, Science, Volume 220, April1983). This mechanism involves the selective absorption of light byvarious chromophores in the body. As these chromophores absorb the lightenergy, they heat up and destroy the surrounding tissue. This tissuedestruction can be used as an alternative therapy to sclerotherapy in abeneficial way to remove unsightly veins and other vascular lesionssince these lesions typically contain one or more highly absorbentchromophores.

The degree of selectivity and therefore tissue damage is dependent uponthe type and amount of chromophore present in the tissue, the depth ofthe target in the tissue, and highly dependent upon the wavelength ofthe light being used. Since lasers are able to provide light in veryprecise wavelength regimes, lasers are ideal instruments forcapitalizing on this principal for treatment of various lesions. Thisselectivity can be very beneficial in that specific lesions containingor surrounded by a particular chromophore(s) can be targeted withspecific wavelengths to provide localized heating and damage whilesparing surrounding tissue lacking the chromophore(s).

In practice however, the light absorption of different chromophores maybe similar. For example, melanin, a chromophore which is found in theepidermis of the skin, may absorb a very similar amount of light energyat some wavelengths as the target tissue (such as the hemoglobin in avein). Therefore, when attempting to deliver sufficiently large amountsof light energy to a target area such as a vein, the melanin in the skinabove the target area may absorb enough light energy to cause epidermaldamage to the skin before the target area has received sufficient energyto cause sufficient damage.

If this epidermal layer, however, is superficially cooled just prior toand/or during the application of the laser energy, the net change intemperature of the chromophores and tissue on the surface will be lessand therefore the collateral damage will be less as well.

It has been known for quite some time that simple cooling techniques canbe used to certain advantage in conjunction with certain therapies,including RF and laser therapies. Such simplistic cooling mechanismsinclude, for example, applying an ice bag to the target area for apredetermined time period prior to the application of therapeutic energyto the target area. It has also been prior described to precool thetarget area, as described above, and alternately provide therapeuticenergy to the target area and a recooling of the target area.

It has been known for quite sometime that various cooling techniques canbe used to protect the device used to provide treatment to a patient.U.S. Pat. No. 4,832,024, issued to Boussignak et al. is one such devicein which a cooling fluid is flowed in a chamber between an optical fiberand the distal emitting end of a cardiovascular catheter. Various otherprior art devices provide a similar cooling of the device, sometimestogether with some resultant cooling of the patient target area. U.S.Pat. No. 4,733,660 issued to Itzkan is such a device in which a coolantis flowed at the distal end of a laser system, such that the laser lightis passed through the liquid coolant, which is passed across theirradiated areas of the patient under treatment. U.S. Pat. No. 3,821,510issued to Muncheryan provides a hand held laser instrumentation devicein which cooling is achieved by evaporation when a coolant is sprayedfrom the laser device to the superficial tissue of the patientundergoing treatment. International Patent Publication WO 97-37723similarly provides a cooling spray directly onto the tissue of thepatient. U.S. Pat. Nos. 5,814,040 and 5,820,628 also spray gas and/orliquid directly onto the skin to provide cooling.

U.S. Pat. Nos. 5,057,104; 5,282,797; and 5,486,172 to Chess providemethods and apparatus for cooling the skin simultaneously with thedelivery of laser light energy. Although lasers and cooling of the skinare involved and discussed, the devices described require a coolingfluid to reside over or be passed over the treatment site during lasertreatment. This requires that the cooling medium be captured between twoseparate transparent windows which can impair visibility of thetreatment area. Proper visualization of the treatment site is veryimportant since many veins are smaller than 100 microns and difficult totarget without excellent visibility of target site. A multi-layer fluidcontainer assembly such as described is expensive, and can impair theability of the practitioner to deliver the light to the appropriatetarget area.

Additionally, if not used correctly, these devices can cause relativelylarge refractive changes in both the incoming laser light (changing thedelivered treatment spot size and therefore the treatment fluences) andin the visible light leaving the target area (making it difficult to aimthe treatment beam correctly).

U.S. Pat. No. 5,344,418 to Ghaffari provides a system with a thermallyconductive optical window which is cooled on one side by a cooled gas(carbon dioxide and Freon™ are mentioned) and in contact with the skinon the other. This system is described to be used in combination with afeedback mechanism to control laser light delivery to the treatmentsite. The cooling mechanism described requires the use of complexdelivery equipment and expensive (and possibly) environmentallyhazardous) materials.

U.S. Pat. No. 4,140,130 to Storm provides a RF system with a coolingelectrode used to direct RF energy to the target and to keep the skincool. However, this system also calls for the cooling fluid to flow overthe target area where the energy is being delivered and relates to RFdevices, not to lasers.

U.S. Pat. No. 3,967,627 to Brown provides a heating and coolingapplicator and control and monitoring circuitry for cooling and heatingareas of the body. This device is not used for laser therapy and alsohas the cooling fluid passing over the entire contact area to be cooled.

SUMMARY

It is an object of this invention to provide a simple device to cool theskin during treatment with electromagnetic energy, including treatmentof vascular and cutaneous lesions, skin disorders, and the removal ofhair.

It is another object of this invention to decrease the complexity of theexisting art and to provide a more economical, cost-effective, and easyto use device. This is accomplished in one embodiment by using athermodynamic property of water or other material called the “latentheat of fusion” to provide a temporary but relatively constanttemperature at the treatment window.

It is still further an object of the present invention to provide asimpler, easier means of visualizing and cooling the target treatmentzone while simultaneously delivering the electromagnetic energy.

It is yet another object of the invention to provide an apparatus whichcan be used for cooling the skin during treatment with electromagneticenergy in areas which are difficult to access with existing art such asthe areas around the nose and ankles.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of one embodiment of the invention;

FIG. 2a is a perspective view of another embodiment of the invention;

FIG. 2b is a cross sectional view of the embodiment of FIG. 2a;

FIG. 3 is a schematic view of the heat transfer mechanism of variousembodiments.

FIG. 4 is a graph depicting temperature verses time for an embodiment ofthis invention; and

FIG. 5 is a view of an alternative embodiment of this invention.

DETAILED DESCRIPTION

The mechanisms for heating the desired tissues during treatment withelectromagnetic energy have been described and it is now established inthe practice that cooling the skin during such treatment reduces patientdiscomfort, allows for higher treatment fluences, and increases theefficacy of the treatment. Such treatments include a treatment of anepidermal layers of the skin, to treat skin disorders, hair removal, andthe treatment of vascular and pigmented lesions.

FIG. 1 is a cross-sectional view depicting one embodiment of thisinvention. FIG. 1 depicts system 100 which includes an energy exit port101, such as a lens or the end of an optical fiber, at the distal end ofa delivery device 120, and a cooling device 110. Cooling device 110allows cooling of the skin in conjunction with exposure toelectromagnetic energy, including laser energy. Such cooling may takeplace before, during, and/or after such exposure to electromagneticenergy.

Port 101 emits electromagnetic energy, such as laser energy, 102, whichis generated in any convenient manner well known to those of ordinaryskill in the art. Energy 102 is directed to a patient target areathrough cooling window 104 of cooling device 110, which in operation isplaced against the area of the patient to be treated. Cooling window 104is in direct contact with the patient's skin, or in contact with theskin via a liquid, gel, or membrane. Cooling window 104 is constructedof a material which is tough yet inexpensive, and provides good thermalconductivity and low absorption of energy 102. Preferably, the materialused to construct window 104 is not hydroscopic. Suitable materials forwindow 104 include many glasses known to those in the laser industryincluding quartz, including polymorphic glass, undoped YAG, diamond, andsapphire, for example being largely transparent to a variety ofelectromagnetic energy 102, for example laser energy in the wavelengthrange between about 0.2 to 3.5 microns. In certain embodiments, a rangeof 400 to 1100 nanometers is used. If desired, window 104 is coated onone or both sides with an anti-reflective coating. Preferably, window104 allows excellent visualization during the procedure, is scratchresistant and is small enough to treat highly contoured areas, such asthose on the face and nose.

Surrounding window 104 is a thermally conductive material 103 which, inthe embodiment of FIG. 1, is thermally coupled to a thermal reservoir105. Thermal reservoir 105 acts as a heat sink and comprises, forexample, a mass of thermally conductive material, if desired the samematerial used to form thermally conductive material 103. In anotherembodiment, thermal reservoir 105 is a cavity containing coolant mediumwhich is chilled prior to the use of cooling device 110. In oneembodiment, thermal reservoir 105 contains a fluid such as water and/orice; carbon dioxide, hydrocarbons, fluorocarbon, chlorofluorocarbons,air, nitrogen, Freon™, gels, or other cooling solids and/or liquidsand/or gasses, which is cooled to a desired temperature or, if desired,frozen prior to use of cooling device 110. In operation, window 104absorbs very little energy 102 passing through it to the patient's skin.By way of example, if sapphire is used as the material for window 104,and window 104 is formed to a thickness of approximately 1 to 20 mm,only about less then one percent of laser energy is absorbed by window104. This small amount of heat absorbed by window 104 is readilyabsorbed by thermally conductive material 103 surrounding window 104 sothat the temperature of window 104 is not increased. More importantly,since window 104 absorbs very little energy from energy beam 102 suchthat its temperature does not rise to any significant degree duringtreatment of the patient, window 104 serves to conduct heat away fromthe patient's skin in the treatment area, thereby preventing discomfortto the patient and enhancing treatment efficacy by allowing a longertreatment period.

The size of thermal reservoir 105 is made to any convenient sizeconsistent with convenient operator utilization and a desired amount ofthermal cooling effect based upon the type of material forming thermalreservoir 105. For greater cooling ability, thermal reservoir 105contains a material capable of changing state, such as, for example,water, which may be frozen prior to the treatment of the patient. Duringtreatment of the patient, this frozen coolant contained within thermalreservoir 105 acts as an excellent coolant device and absorbssignificant amounts of heat as the state changes from solid to liquidand the latent heat of fusion is absorbed by the coolant material duringthis change of state. Alternatively, gas such as air, nitrogen, CO₂, ora cryogenic gas is used as the coolant material. In other embodiments, agas is used which is cooled to a liquid or solid state, allowing thelatent heat of vaporization and/or the latent heat of fusion to be usedin achieving the desired cooling effect.

The present invention has been designed specifically to cool the surfaceof the skin before, during and after laser exposures. Like other activecooling devices used in dermatology, the present invention significantlylowers the temperature of the epidermis and the dermal-epidermaljunction. The lower temperature facilitates higher treatment fluencesand reduces the thermal damage to non-target tissue, which significantlyreduces side effects such as transitory hyper- or hypo-pigmentation. Thepresent invention significantly reduces the pain experienced bypatients. Unlike other cooling technologies, this embodiment of thepresent invention does not require the use of expensive cryogeniccanisters or chillers and does not use cumbersome hoses to providecooling. FIG. 3 shows a magnified cross sectional view of a cooling tipin contact with skin with arrows indicating the flow of heat from theepidermis, to the sapphire window and the cooling reservoir.

To fully appreciate the advantages of the present invention compared toother active cooling devices, it is important to understand how itworks. One embodiment of the present invention utilizes the large latentheat of fusion of water (79.71 calories/gram) to maintain the skin at aconstant low temperature for long periods of time. Because it requiresso much energy to melt ice, the 13.1 grams of ice in the reusable tipshave more heat capacity than 1.0 liters of liquid water at 0 degreesCelsius. As the ice melts, the temperature of the reservoir in thepresent invention is maintained at 0 degrees Celsius. for an average of20 minutes under normal operating conditions. This allows the window ofthe present invention to maintain a constant temperature of 15° C. orlower, for 20 minutes, while being traced over the skin at a rate of 1cm/second, in a 25° C. room, with 100 watts of laser light directedthrough the sapphire window. When used in this manner, most of the heatremoved by the present invention is not from the laser light absorbed attissue, but rather from ordinary body heat (approximately 0.2 to 1calorie/second are transferred from the epidermis to the sapphirewindow). After 20 minutes have elapsed, the cooling tip can be easilyreplaced with another frozen cooling tip. Thus, the four cooling tipssupplied with the present invention provide 1 hour and 20 minutes ofcooling that can be “recharged” by placing them in a freezer for 30minutes and thus, allowing continuous laser treatment. FIG. 4 shows thetemperature of the window in one embodiment of the present inventionwhich does not utilize any pipping or flowing of the coolant, over a 30minute time interval. The constant temperature during the 4-24 minutetime period is due to the presence of ice in the reservoir of thisembodiment. Only after all the ice in the reservoir has melted does thetemperature begin rising to room temperature.

In one embodiment, one or more temperature sensors are placed in thermalcontact with one or more of window 104, thermally conductive material103, and thermal reservoir 105. In one such embodiment, the temperaturesensor is made of color changing liquid crystals or the like.

In one embodiment, system 100 includes, if desired, a bracket 106 suchthat the cooling device including cooling window 104 is attached to thedistal end 101 of the delivery system, thereby allowing easy operatormanipulation. In one embodiment bracket 106 is detachable from one orboth of delivery system 120 and cooling device 110, to permit coolingdevice 110 to be easily removed for precooling, or use on other deliverysystems.

In certain embodiments, a good thermal bond is made between coolingwindow 104 and surrounding thermally conductive material 103. Smoothsurfaces to provide for a press or snap fit of window 104 intosurrounding thermally conductive material 103 enhance thermalconductively therebetween. In alternative embodiments, thermal epoxy,brazing, or soldering is used to secure cooling window 104 to thermallyconductive material 103 and provide good heat transfer therebetween. Inalternative embodiments, thermally conductive material 103 is platedwith a low allergic reaction material, such as gold plated copper.

FIG. 2a is a perspective view of an alternative embodiment of thepresent invention. Electromagnetic energy system 200 of FIG. 2a includeselectromagnetic energy delivery device 220 which receives energy, forexample, laser energy, via optical fiber 221 and emits energy 202 fromits distal end. Energy 202 is directed to a patient target area throughcooling window 204 of cooling device 210. At least surrounding coolingwindow 204 is thermally conductive material 203 which conducts thermalenergy from the patient's treatment area as such heat is absorbed bycooling window 204. The heat thus absorbed by cooling window 204 and bythermally conductive material 203 is conducted to thermal reservoir 205contained within handpiece 290. Handpiece 290 of cooling device 210 is,if desired, attached to electromagnetic energy delivery device 220 suchthat system 200 is conveniently manipulated as a single unit. In oneembodiment, this attachment is provided as a detachable engagement suchthat cooling unit 210 and electromagnetic energy deliverable device 220can be separating for cleaning, maintenance, or the precooling ofcooling device of 210 prior to use in a medical procedure. In oneembodiment of this invention, cooling device 210 includes hand piece 290which is detachably connected to cooling tip 289 via a detachableconnection 291.

FIG. 2b depicts a cross sectional view of one embodiment of thisinvention similar to that shown in perspective view of FIG. 2a, withcommon reference numerals. As shown in FIG. 2b, electromagnetic energydelivery device 220 includes electromagnetic energy exit port 201, suchas a lens or an optical fiber. The connection between theelectromagnetic energy delivery device 220 and hand piece 290 is shownby reference numeral 250. As shown in FIG. 2b, hand piece 290 in thisembodiment includes a thermal reservoir 205 which contains a coolingmedium. In one embodiment, this cooling medium is self contained, and iscooled prior to use of cooling device 290. In this embodiment, thematerial contained within thermal reservoir 205 is formed of anyconvenient material capable of absorbing thermal energy, includingvarious metals or the like. Alternatively, thermal reservoir 205contains a liquid, such as water, or a gas such as air, nitrogen, CO₂,or cryogenic gas. As previously described, in certain embodimentsmaterial contained within thermal reservoir 205 is capable of changingstate, thereby allow the latent heat fusion and/or the latent heatvaporization to be used to absorb thermal energy from the patient's skinvia cooling window 204 and thermally conductive material 203.

In one embodiment, as depicted in FIG. 2b, an inlet port 271 and anoutlet port 272 are used to circulate cooling material (i.e. liquid orgas) either directly into thermal reservoir 205, or to a chambersurrounding thermal reservoir 205, in order to allow cooling medium tobe circulated to handpiece 290, in turn gathering thermal energyabsorbed from a patient's skin. If desired, this cooling material ischilled and recirculated, for example by use of a chiller orthermoelectric cooler and pump system. Alternatively, cooling materialis simply obtained from a cool source and disposed of after absorbingheat from cooling device 290.

FIG. 3 is a schematic representation of heat from a patent's tissuebeing absorbed by thermal window 304 and transmitted to thermallyconductive material 303 for absorption by thermal reservoir 305.

As shown in FIG. 3, heat is absorbed from the patient's tissue by window304 and conducted by thermal conductive material 303 to reservoir 305containing coolant. As depicted in FIG. 3, in accordance with theteachings of the present invention, a simple and cost effectivemechanism is provided for cooling patient's skin before, during, and/orafter electromagnetic energy treatment, without the need for expensiveand complex equipment, such as described in the prior art. Thus, nosmall and expensive tubes are required to pump coolant to regionsdirectly surrounding the window. In contrast, in accordance with theteachings of this invention, a simple and cost effective structure isprovided which adequately removes heat absorbed from the patient'stissue by the window, by simple thermal conductivity through non-flowingthermally conductive material to a coolant reservoir. The coolantreservoir contains adequate cooling capability to allow effective use inmedical procedures without the need for expensive cooling arrangements.

In one embodiment of this invention, as depicted in FIG. 5, coolant isflowed through a small region 401 of device 400, in order to remove heatfrom window 404 via thermally conductive material 403. As shown in FIG.5, even though a flowing coolant is used in this embodiment, the costeffectiveness is maintained by providing that the coolant flows onlythrough a small portion 401 of the device, and not in a highly machinedand expensive piping system surrounding window 404.

In one embodiment of this invention, as depicted in FIG. 5, coolant isflowed through a small region 401 of device 400, in order to remove heatfrom window 404 via thermally conductive material 403. Device 400 can bemade from gold plated copper. As shown in FIG. 5, even though a flowingcoolant is used in this embodiment, the cost effectiveness is maintainedby providing that the coolant flows only through a small portion.401 ofthe device, and not in a highly machined and expensive piping systemsurrounding window 404. Specifically, handle 406 of device 400 isprovided with one or more channels for providing a flow path notadjacent to, and thus spaced from, an edge of window 404. Coolant entersSuch one or more channels through an inlet port 407 and exits handle 406through an outlet port 408.

All publications and patent applications mentioned in this specificationare herein incorporated by reference to the same extent as if eachindividual publication or patent application was specifically andindividually indicated to be incorporated by reference.

The invention now being fully described, it will be apparent to one ofordinary skill in the art that many changes and modifications can bemade thereto without departing from the spirit or scope of the appendedclaims.

What is claimed is:
 1. An apparatus for lowering the temperature of skinon a patient during treatment applying electromagnetic energy to theskin, comprising: a window of a first thermally conductive materialthrough which electromagnetic energy can pass for placement against theepidermis of the skin; a reservoir of coolant spaced from an edge ofsaid window; and a non-flowing second thermally conductive materialconnecting said window and said reservoir to transfer heat from saidwindow to said coolant in said reservoir.
 2. The apparatus of claim 1,wherein said second thermally conductive material at least partiallysurrounds said window.
 3. The apparatus of claim 1, wherein said windowis transparent to laser light.
 4. The apparatus of claim 1, wherein saidfirst thermally conductive material is substantially transparent in thewavelength range from 400 to 1100 nanometers and has good heat transferproperties.
 5. The apparatus of claim 4, wherein said first thermallyconductive material is selected from the group consisting of sapphire,quartz and polymorphic glass.
 6. The apparatus of claim 1, wherein saidcoolant is selected from the group consisting of a liquid, water, air,nitrogen, CO₂, a cryogenic gas and ice water.
 7. The apparatus of claim1, wherein good thermal contact between said window and said secondthermally conductive material is accomplished by brazing, bonding,gluing, soldering, or mechanically compressing said window to saidsecond thermally conductive material.
 8. The apparatus of claim 1,further comprising one or more temperature sensors in thermal contactwith one or more of said window, said second thermally conductivematerial, and said reservoir.
 9. The apparatus of claim 8, wherein atleast one of said one or more temperature sensors is a color changingmaterial.
 10. The apparatus of claim 1, wherein said first thermallyconductive material is substantially transparent to electromagneticradiation between 0.2 and 3.5 microns and has good heat transferproperties.
 11. The apparatus of claim 10, wherein said window is coatedon one or more surfaces with an antireflection coating.
 12. Theapparatus of claim 10, wherein said first thermally conductive materialis selected from the group consisting of diamond, sapphire, quartz andglass.
 13. The apparatus of claim 1, wherein said first thermallyconductive material is substantially transparent to radio-frequency andmicrowave radiation and has good heat transfer properties.
 14. Theapparatus of claim 13, wherein said window is coated on one or moresurfaces with an antireflection coating.
 15. The apparatus of claim 13,wherein said first thermally conductive material is selected from thegroup consisting of diamond, sapphire, quartz and glass.
 16. Anapparatus for use with a coolant to lower the temperature of skin on apatient during treatment applying electromagnetic energy to the skin,comprising: a window of a first thermally conductive material throughwhich electromagnetic energy can pass for placement against theepidermis of the skin; a handle having one or more channels forreceiving the coolant and providing a flow path spaced from an edge ofsaid window; and a non-flowing second thermally conductive materialconnecting said window and said handle to transfer heat from said windowto coolant contained in said one or more channels.
 17. The apparatus ofclaim 16, wherein said second thermally conductive material at leastpartially surrounds said window.
 18. The apparatus of claim 16, whereinsaid window is transparent to laser light.
 19. The apparatus of claim16, wherein said first thermally conductive material is substantiallytransparent in the wavelength range from 400 to 1100 nanometers and hasgood heat transfer properties.
 20. The apparatus of claim 19, whereinsaid first thermally conductive material is selected from the groupconsisting of sapphire, quartz and polymorphic glass.
 21. The apparatusof claim 16, wherein said coolant is selected from the group consistingof a liquid, water, air, nitrogen, CO₂, a cryogenic gas and ice water.22. The apparatus of claim 16, wherein good thermal contact between saidwindow and said second thermally conductive material is accomplished bybrazing, bonding, gluing, soldering, or mechanically compressing saidwindow to said second thermally conductive material.
 23. The apparatusof claim 16, further comprising one or more temperature sensors inthermal contact with one or more of said window, said second thermallyconductive material, and said one or more channels.
 24. The apparatus ofclaim 23, wherein at least one of said one or more temperature sensorsis a color changing material.
 25. The apparatus of claim 23, furthercomprising a control device responsive to said one or more temperaturesensors for adjusting the flow and/or temperature of coolant in said oneor more channels.
 26. The apparatus of claim 25, further comprising arefrigeration mechanism for cooling and recirculating said coolant. 27.The apparatus of claim 16, wherein said first thermally conductivematerial is substantially transparent to electromagnetic radiationbetween 0.2 and 3.5 microns and has good heat transfer properties. 28.The apparatus of claim 27, wherein said window is coated on one or moresurfaces with an antireflection coating.
 29. The apparatus of claim 27,wherein said first thermally conductive material is selected from thegroup consisting of diamond, sapphire, quartz and glass.
 30. Theapparatus of claim 16, wherein said first thermally conductive materialis substantially transparent to radio-frequency and microwave radiationand has good heat transfer properties.
 31. The apparatus of claim 30,wherein said window is coated on one or more surfaces with anantireflection coating.
 32. The apparatus of claim 30, wherein saidfirst thermally conductive material is selected from the groupconsisting of diamond, sapphire, quartz and glass.
 33. The apparatus of16 further comprising a refrigeration mechanism coupled to said handlefor cooling and recirculating said coolant.
 34. An apparatus for usewith a coolant to lower the temperature of skin on a patient during atreatment applying laser energy to the skin, comprising a body of atleast one nonflowing first thermally conductive material, a window of asecond thermally conductive material through which the laser energy canpass attached to the body for placement against the epidermis of theskin, the body being provided with a flow channel through which thecoolant can pass to transfer heat from the window and the body duringthe treatment.
 35. The apparatus of claim 34 for use with a laserproviding a laser beam wherein the body includes means for securing thelaser to the body so that the laser beam passes through the window. 36.The apparatus of claim 35 wherein the second thermally conductivematerial is sapphire.
 37. The apparatus of claim 36 wherein the bodyincludes a layer of thermal epoxy in the vicinity of the window.
 38. Theapparatus of claim 34 wherein the body includes a handpiece.